The Functional Brain Imaging Core will provide the scientific environment, imaging resources, and data analysis support to conduct three novel pilot investigators of late-life mood disorders using functional imaging. Each imaging study will examine a specific biological hypotheses related to late-life mood disorders using functional imaging method that share two or more of the following innovative attributes: a) measurement of the change in regional brain function during a pharmacological or sensory probe; b) examination of the remitted patient to allow focus on potential trait- related attributes; or c) examination of a specific receptor system putatively related to the manifestion of mood disorders in the elderly. Objectives of the three proposed pilot projects are; Study 1: Identify circadian timing system abnormalities in remitted late-life depressed patients using a bright light stimulus. Study 2: Determine the relationships between the regional brain serotonin-mediated responses to a serotonergic challenge, CSF 5-HIAA as a measure of overall serotonin innervation, and suicidality and hopelessness in late-life depressed patients. Study 3; Identify changes in regional serotonin reuptake )serotonin transporter) sites in elderly depressed patients.